Question 1

Do the Duke Criteria apply to prosthetic valve endocarditis?

Accepted Answer

Yes, though sensitivity is lower. The modified Duke Criteria (2000 update) include echocardiographic findings specific to prosthetic valves. FDG-PET/CT and cardiac CT are increasingly used as major criteria in this population.

Question 2

How does S. aureus bacteraemia affect the score?

Accepted Answer

S. aureus bacteraemia in the setting of a prosthetic valve or intracardiac device qualifies as a major criterion even without echocardiographic evidence, provided there is no alternative source. This is a key modification from the original criteria.

Question 3

Can IE be diagnosed with negative blood cultures?

Accepted Answer

Yes — culture-negative IE accounts for 5–15% of cases, most often due to prior antibiotic use or fastidious organisms (Coxiella burnetii, Bartonella, Tropheryma whipplei, HACEK). Serology and PCR may provide microbiological evidence that contributes as either a major or minor criterion.